1. Field of the Invention
The present invention relates to a thermochromic window, and more particularly, to a thermochromic window, the infrared (IR) transmittance of which is adjusted depending on the temperature.
2. Description of Related Art
Thermochromism refers to the phenomenon in which an oxide or a sulfide of a transition metal undergoes a change in its crystalline structure below and above a specific temperature (i.e. its transition temperature (Tc)), whereby its physical properties (electrical conductivity and infrared (IR) transmittance) significantly change.
When a glass is coated with a thin film that has such thermochromic capability, a “smart window” can be produced, which transmits visible light but blocks near infrared (NIR) radiation and infrared (IR) radiation at or above a predetermined temperature in order to prevent the indoor temperature from increasing. The application of smart windows to vehicles or buildings may be very effective in saving energy.
Materials that exhibit thermochromism include oxides of several transition metals, of which vanadium dioxide (VO2) is being widely studied since its transition temperature is 68° C., which is relatively close to the temperature at which practical application becomes possible.
When such a thermochromic thin film is applied to an architectural glass, low emissivity is required in order to minimize heat loss when warming is conducted in winter. However, the traditional thermochromic thin film does not have low emissivity, which is problematic. In particular, a vanadium dioxide (VO2) thin film has a problem in that it cannot effectively insulate heat when warming is conducted in winter since it has high emissivity of 0.84 that is similar to that of typical glass.
The information disclosed in the Background of the Invention section is only for better understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.